The present invention relates to internal combustion engine turbochargers and exhaust gas re-circulation systems, and, more particularly, to an internal combustion engine having multiple exhaust gas manifolds, a twin turbine turbocharger and an exhaust gas re-circulation system.
An internal combustion engine may include one or more turbochargers for compressing a fluid to be supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine, and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chambers. The fluid compressed by the compressor may be in the form of combustion air only, or may be a mixture of fuel and combustion air.
It is known to provide multiple turbochargers within a turbocharger system in an internal combustion engine. For example, U.S. Pat. No. 3,250,068 (Vulliamy) discloses an internal combustion engine having two turbochargers. A first turbocharger includes a turbine which is driven by a single exhaust manifold on the internal combustion engine. The spent exhaust gas from the turbine of the first turbocharger is transported in a series manner to the inlet of a turbine of the second turbocharger. The spent exhaust gas is then discharged to the ambient environment from the turbine of the second turbocharger. The compressor of the second turbocharger compresses ambient combustion air and provides the compressed combustion air in a series manner to the compressor of the first turbocharger, which in turn transports the compressed combustion air to the intake manifold of the engine.
A problem with a turbocharger system as described above is that the spent exhaust gas from the turbine of the first turbocharger may not have enough energy to provide a desired compression ratio within the second turbocharger. The overall compression ratio from the turbocharger system is thus limited according to the amount of energy available at the turbine of the second turbocharger.
An exhaust gas re-circulation (EGR) system is used for controlling the generation of undesirable pollutant gases and particulate matter in the operation of internal combustion engines. Such systems have proven particularly useful in internal combustion engines used in motor vehicles such as passenger cars, light duty trucks, and other on-road motor equipment. EGR systems primarily re-circulate the exhaust gas by-products into the intake air supply of the internal combustion engine. The exhaust gas which is reintroduced to the engine cylinder reduces the concentration of oxygen therein, which in turn lowers the maximum Combustion temperature within the cylinder and slows the chemical reaction of the combustion process, decreasing the formation of nitrous oxides (NOx). Furthermore, the exhaust gases typically contain unburned hydrocarbons, which are burned on reintroduction into the engine cylinder, further reducing the amount of exhaust gas by-products emitted as undesirable pollutants from the internal combustion engine.
Dependent upon certain operating conditions associated with a diesel engine, it may be desirable to provided a richer or leaner mixture of the exhaust gas within the combustion air which is transported to the intake manifold. One known technique for controlling the amount of exhaust gas which is mixed with the combustion air utilizes controllably actuatable valves which interconnect the exhaust manifold with the compressor which receives the exhaust gas. The flow of exhaust gas to the second compressor can be completely shut off, or can be controlled on a timed basis to provide a desired average flow of exhaust gas which mixes with the combustion air. Another known technique is to provide a bypass fluid conduit associated with the combustion air or exhaust gas. A controllably actuatable butterfly valve or the like is positioned within the bypass fluid conduit and controlled to in turn control the amount of exhaust gas which mixes with the combustion air. Although such systems are effective to control exhaust gas re-circulation within the diesel engine, they usually require that additional structure in the form of sensors, conduits, valves and associated controllers be added to the internal combustion engine.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, an internal combustion engine is provided with a plurality of combustion cylinders, a first exhaust manifold and a second exhaust manifold each coupled with a plurality of the combustion cylinders, and at least one intake manifold coupled with a plurality of the combustion cylinders. A first turbocharger includes a first turbine having at least one inlet and an outlet, and a first compressor having an inlet and an outlet. The at least one first turbine inlet is fluidly coupled with the first exhaust manifold. A second turbocharger includes a second turbine having an inlet and an outlet, and a second compressor having an inlet and an outlet. The inlet of the second turbine has a controllable, variable intake nozzle and is fluidly coupled with the second exhaust manifold. The second compressor inlet is fluidly coupled with the first compressor outlet.
In another aspect of the invention, a turbocharger system is provided, for use with an internal combustion engine having a plurality of combustion cylinders, an intake manifold and first and second exhaust manifolds. The turbocharger system has a first turbocharger including a first turbine having at least one inlet and an outlet, and a first compressor having an inlet and an outlet. The at least one first turbine inlet is fluidly coupled with the first exhaust manifold. A second turbocharger includes a second turbine having an inlet and an outlet, and a second compressor having an inlet and an outlet. The second turbine inlet is fluidly coupled with the second exhaust manifold and has a controllable, variable intake nozzle. The second compressor inlet is fluidly coupled with the first compressor outlet.
In yet another aspect of the invention, a method of operating an internal combustion engine is provided with the steps of: providing a plurality of combustion cylinders, an intake manifold supplying combustion gas to said plurality of combustion cylinders and first and second exhaust manifolds; transporting exhaust gas from the plurality of combustion cylinders to the first exhaust manifold and the second exhaust manifold; providing a first turbocharger including a first turbine having at least one inlet and an outlet, and a first compressor having an inlet and an outlet; providing a second turbocharger including a second turbine having a controllable, variable inlet and an outlet, and a second compressor having an inlet and an outlet; rotatably driving the first turbine with exhaust gas introduced at the first turbine at least one inlet from each the second turbine outlet and the first exhaust manifold; rotatably driving the second turbine with exhaust gas introduced at the second turbine inlet from the second exhaust manifold; introducing combustion gas at the first compressor inlet; transporting compressed combustion gas from the first compressor outlet to the second compressor inlet; transporting compressed combustion gas from the second compressor outlet to the intake manifold; sensing at least one of operating conditions of the engine and performance of the turbochargers; and controlling the controllable, variable intake nozzle in response to at least one of the engine operating conditions and the performance of the turbochargers.
In still another aspect of the invention, a turbocharger and engine emission control system is provided for use with an internal combustion engine having a plurality of combustion cylinders, an intake manifold and first and second exhaust manifolds. A first turbocharger includes a first turbine having at least one inlet and an outlet, and a first compressor having an inlet and an outlet. The at least one first turbine inlet is fluidly coupled with the first exhaust manifold. A second turbocharger includes a second turbine having an inlet and an outlet, and a second compressor having an inlet and an outlet. The second turbine inlet has a controllable, variable intake nozzle and is fluidly coupled with the second exhaust manifold. The second compressor inlet is fluidly coupled with the first compressor outlet. An EGR duct is fluidly coupled to the second exhaust manifold and to the intake manifold.